Variable condenser construction



q Z4, 1940- A. HOROWITVZ 2,215,791

VARIABLE CONDENSER CONSTRUCTION Filed June 9, 195a 2 Sheets-Sheet 1 I NV EN TOR. ALEX NDRE HOROW/TZ ATTORNEY.

Sept. 24, 1940. A. HbROWlTZ VARIABLE CdNDENSER CONSTRUCTION Filed June 9. 19587 v INVENTOR. I

' LEXANDREHOROW/TZ BY v ATTORNEY.

2 Sheets-Sheet 2 Patented Sept. 24,

PATENT} oFiucr.v

VARIABLE CONDENSER QONSTRUCTION Alexandre Horowitz, Eindhoven, Netherlands, assignor, by mesne assignments, to Radio Corporporation of America, New York, NJ Y., a. corporation of Delaware Application June 9, 1935, Serial No. 212,693

In the Netherlands July 16, 1937 g 2 Claims.

As regards to rotary shafts present in electric apparatus it ls frequently desirable that they should be journalletl in the apparatus so as to have practically no play and, besides, to be selfcentering. Such is particularly the case if such or a permanent displacement of the latter from its normal position results in an undesirable uncontrollable alteration of the capacity of the condenser. According to the invention, these drawbacks are avoided.

The invention relates to an electric apparatus such as a radio-receiving apparatus wherein one or more of the rotary shafts present in the apparatus are journalled so as to have substantially no play and, besides, to be self-centering in a ballbearing whose balls runln a path which is formed by a couple of conical contact surfaces on the shaft in question and by a couple of similar contact surfaces in the stationary portion of the bearing, one of the latter contact surfaces being slightly movable with respect to the other contact surfaces and being forced by resiliency against the balls.

The electric apparatus may be of very diiferent character. In addition to radio receiving apparatus there may also be considered, for ex ample, measuring tables, in general that group of apparatus wherein for some reason or other it is desirable that the rotary shafts should be journalled without any play and be automatically centered.

Concerning the action of the playless, 'selfcentering bearing according to the invention the following may be observed. In the assumption that the shaft considered is not removed from its central position by a non-excessive load, the return of this. shaft into its original position, after an axial overload, due to which the shaft has consequently been removed from its central position, has ceased, has to be imagined to take place in such manner that, after the overload has ceased, this shaft is restored to its original position due to the co-operation of the movable contact surface, the balls and the contact surface in the shaft, which is located diametrically opposite the movable surface and to the fact that the movable surface is pressed by resiliency against the balls. Besides, the points of contact of the balls with one of the contact surfaces will always be located on-a conic section which is determined by the cutting of the contact surface under consideration by the plane which comprises the points of contact of the balls. The position of equilibrium of the balls is attained when the conic section assumes the shape of a circle. The balls always tend to occupy this position of equilibrium. If the shaft is'radlally overloaded, due to which the shaft consequently makes an angle with the centre-line of the shaft in iits normal position, the points of the balls which are in contact with one of the contact surfaces will come to lie on a conic section difierent from the circle of equilibrium for example on an ellipse. When the radial overload ceases to exist the balls will occupy again their position of equilibrium. In

this case the points of the balls which are in contact with one of thecontact surfaces come to lie again on a circle, with the result that the shaft occupies again its original central position in the bearing. The above-described construction permits to manufacture a cheap, self-centering bearing which is practically without any play, from components which need no particular further treatment, such in contradistinction to the ball-bearings which, in order to have at the utmost a clearance of a few thousa'ndths of a millimetre, require a very careful further treatment, in the present case regrindlng of the contact surfaces, which entails of course considerable costs.

The apparatus according to the invention may have a bearing whose movable contact surface is secured, through the intermediary of one or more resilient washers, to the fixed portion of the hearing. These washers ensure in this case that the balls are forced by resiliency against the contact surfaces. According to the invention, this effect may also be obtained by making the movable contact surface itself somewhat resilient and, if. desired, by securing such a resilient contact surface to the bearing also through the intermediary of one or more resilient washers.

The contact surfaces are preferably so formed that their generating lines makes angles of from 30 to with the centre-line of the shaft Journalled in the hearing when it occupies its central position. 'It is advisable that the angles formed by these lines pertaining to the contact surfaces in the fixed portion of the hearing or to the shaft are two by two mutually equal. slip ofthe balls with respect-to the contact surfaces being thus avoided.

The number of balls utilised in the bearing may in general be chosen at will. If the load on the shaft is not too large, it is advisable, in accordance with the invention, to journal the shaft on three balls owing .to which a statically determined J'ournalling of the shaft is obtained. These balls are'preferably kept spaced apart by a ball race. The shaft journalled in the bearing may of course be hollow or solid.

The journalling above described is particularly advantageous for supporting a variable condenser present in the apparatus according to the invention, which maybe formed, for example, either as a rotatable or as a slidable condenser.

The invention will be explained more fully with reference to the accompanying drawing wherein Figure 1 represents across-section of a slidable condenser present in the apparatusaccord ing to the invention. Fig. 2 is a plan view of Fig. 1. Fig. 3 is a cross-sectional view, on an enlarged scale, of the bearing at the operating end of the condenser frame. Fig. 4 is a crosssectional view, on an enlarged scale, of the bearing taken along the line 4-4 of Fig. 3, and

Fig. 5 .is a detailed view in cross-section of the ball raceway.

Thecondenser illustrated is of the'triple section type and is mounted within a casing i having three compartments which are separated from one another by partitions2 and 3. The front wall of the casing is denoted by 4 and the rear wall by 5. The partitions within the casing have all of them a central bore through which passes a shaft 6 having rigidly mounted on it slidable condenser halves 1, 8 and 9. A motion of the shaft 6 in axial direction consequently results in a similar displacement of the condenser halves 1, 8 and 9. Stationary condenser halves l2, l8 and I4 are mounted on two supporting,

be moved with respect thereto without any objection.

At its left-hand end the shaft 8 is clamped in a bush 8 provided with a screw thread NJ in which a ball 20 can be displaced. This ball protrudes through an aperture 2| provided in the actuating knob 2| and is pressed into the groove l9 with the aid of an annular blade spring 28'. Owing to the bevelled shape of the walls of the groove l9 and to the pressure exerted by the spring 20' the ball 28 has no play in the groove IS. The actuating knob 2|, which has the shape of a hollow bush or shaft, is journalled in a ball bearing 24 in the front plate 4 of the condenser. The actuating knob 2| can only be turned with respect to the condenser casing, owing to the presence of the ball bearing 24, and cannot be displaced in axial direction. A rotatory motion of this knob brings about a displacement of the ball 20 in the groove IS with the result that the shaft 6 is axially displaced and that each of the movable condenser halves is displaced with respect to the corresponding fixed halves, the alteration of the capacity being thus effected. During this For the sake of simplicity the journalle'dshaft 2| is represented in Figure 3 as a hollow bush.

In this shaft is provided an annular groove 22 Whose walls are formed by conical surfaces 22a and 22b and a bottom portion 220. The front wall 4 of the casing of the condenser has secured to it a rigid ring 23 which is formed with a conical contact surface 23. Furthermore the front wall 4 has secured to it, by means of resilient washers 25, another rigid ring 26 which is provided on the inside with a conical contact sur face 21. Between the surfaces 22a, 22b, 23' and 21 are clamped three balls 28 which are kept spaced apart by a ball race 29 which has to that end recesses 30. The attachment of the rings 2;

and 28 to the front plate 4 of the condenser is eifected by means of stud bolts 3|. With this construction the contact surface "is the movable one. Owing to the resiliency of the washers 25 it is permanently pressed against the balls 28.

Although the'balls are spacedapart by a distance corresponding to an angle at the centre of 120. Figures 1 and 3 show for the sake of clearness two balls.

A displacement of the-shaft 2| to the right (see the direction of the arrow A in Fig. 3) is excluded owing to the fact that the ring 23 is rigid and is immovably secured to the wall 4. If the shaft I would be displaced, due to an overload, in the direction of the arrow B, the resilient washers 25 ensure, jointly with the ring 28, that, after this overload has ceased to exist, the shaft returns again to its original position. In the case of a radial overload on the shaft 2|, for example in the direction of the arrow C, the points with which each of the balls is in contact with one of the contact surfaces are displaced in such manner that the, circle of contact with one of the contact surfaces merges into a conic section whose plane isno. longer perpendicular to the center-line of the shaft 2|. The balls have consequently left their position of equilibrium and when the overload C ceases to exist they will return, owing to the action of the resilient washers 25 and to the conical shapeof the contact surfaces, to their position of equilibrium, which results in that the shaft is automatically restored to its original position, the shaft being consequently self-centering. Also during this displacement the ring 26 and therefore the contact surface 21 have first left their position of equilibrium and then returned into this position.

It appears from Fig. 5 that it is advantageous that the angles formed by the surfaces 22a and 22b on the one hand and the surfaces28' and 21 on the other hand with respect to the axis X-Y of the ball and therefore with respect to thecenter-line of the journalled shaft are mutually equal two bytwo. The generating lines of the surfaces 22a, 221) form an angle a with the .axis of revolution X,Y of each ball whereas the surfaces 23' and 21 each form an angle b with the axis X--Y. It is thus ensured that the distance of the point of contact of each of the balls with the surface 22a, 22b from the axis X--Y acquires the same value 0 whereas for the surfaces 23' and 21 this distance has a value if, slip of the shaft being thus avoided.

From the above it will be clear that the journalling according to Figs. 3 and 4 may be utilised with great advantage in the condenser described with reference to Figs. 1 and 2 for supporting 16 the shaft or bush 2|. Any radial or axial overload of the knob 2! with the aid of which the condenser is adjusted, consequently has, after this overload has ceased to exist, no influence on the position of the movable portion of the condenser with respect to the fixed portion thereof since the shaft 2| is self-centering. Any play is suppressed since owing vto the fact that the balls are pressed by resiliency, any play is absorbed in the bearing 24; neither has the ball 20 any play in its path.-

What I claim is: I 4

1. In a tuning condenser provided with an end plate and a rotor shaft, a bearing for iournalling the shaft in said end plate whereby it is capable its outer periphery, the inner peripheral portions of said disk members being formed to provide conical contact surfaces, balls provided in the sleeve race-way and cooperating with the disk contact surfaces, and a retaining member for the balls.

2.'In a tuning condenser provided with an end plate and a control shaft, a hollow sleeve serving as a control member for the control shaft provided with a race-way'on its outer surface. the

I control shaft extending into said hollow sleeve,

means for laterally moving the control shaft upon rotation ofthe hollow sleeve control member, a pair of annular disk members, one of which has its outerperiphery rigidly mounted on the end plate, means for resiliently mounting the other disk member at its outer periphery, the inner peripheral portions of said disk members being .iormed to provide conical contact surfaces, balls provided in the sleeve race-way and cooperating with the disk contact surfaces, and a retaining member for the balls.

HOROWITZ. 

